Hydrolysis of O-Acetylsalicylic Acid (Aspirin) in Relation to the Aspirin-Bromate-Acid Oscillating System

2006 ◽  
Vol 71 (10) ◽  
pp. 1445-1452 ◽  
Author(s):  
Ľubica Adamčíková ◽  
Daniel Mišicák ◽  
Peter Ševčík
Keyword(s):  
Acetic Acid ◽  
Salicylic Acid ◽  
Acetylsalicylic Acid ◽  
Induction Period ◽  
Rate Constant ◽  
Degradation Products ◽  
Oscillatory Behavior ◽  
Active Substrate ◽  
Hydrolysis Of

The uncatalyzed BrO3--O-acetylsalicylic acid (aspirin) reaction in aqueous H2SO4 exhibits oscillatory behavior. The induction period observed before the onset of oscillations depends on the extent of hydrolysis of aspirin. The rate constant of hydrolysis of aspirin was determined indirectly from the value of induction period. When aspirin undergoes hydrolysis, the degradation products are salicylic acid and acetic acid. Salicylic acid may play a role of "active" substrate responsible for the oscillations. Aspirin (Bayer) generates also oscillations with bromate.

scholarly journals Kinetics and Mechanism of Hydrolysis of Acetylthiocholine by Butyrylcholine Esterase

2002 ◽  
Vol 57 (11-12) ◽  
pp. 1072-1077 ◽  
Author(s):  
Karel Komers ◽  
Alexandr Čegan ◽  
Marek Link
Keyword(s):  
Acetic Acid ◽  
Kinetics And Mechanism ◽  
Kinetics Parameters ◽  
Mechanism Of Hydrolysis ◽  
Ph Stat ◽  
Stat Method ◽  
Ellman’S Method ◽  
Hydrolysis Of

Kinetics and mechanism of hydrolysis of acetylthiocholine by the enzyme butyrylcholine esterase was studied. The spectrophotometric Ellman’s method and potentiometric pH-stat method were used for continuous determination of the actual concentration of the products thiocholine and acetic acid in the reaction mixture. The validity of the Michaelis-Menten (Briggs-Haldane) equation in the whole course of the reaction under used conditions was proved. The corresponding kinetics parameters (Vm and KM) were calculated from the obtained dependences of concentration of thiocholine or acetic acid vs. time and compared. From this comparison the deciding kinetic role of the step producing thiocholine was derived. The values of initial molar concentration of the enzyme and of the rate constants of the kinetic model were estimated.

Hydrolysis of Zirconium Propoxide by an Esterification Reaction

1992 ◽  
Vol 271 ◽  
Author(s):  
I. Laaziz ◽  
A. Larbot ◽  
C. Guizard ◽  
A. Julbe ◽  
L. Cot
Keyword(s):  
Acetic Acid ◽  
Light Scattering ◽  
Crystalline Structure ◽  
Structure Determination ◽  
Nmr Spectra ◽  
Esterification Reaction ◽  
Zirconium Propoxide ◽  
Size Growth ◽  
Hydrolysis Of

ABSTRACTZirconium propoxide hydrolysis was performed with the help of an esterification reaction using acetic acid. Products, obtained according to the value of hydrolysis ratio, are successively crystals, sols and gels or precipitates. The similarity of FUR and NMR spectra for crystals and gels allows to think that the arrangements of ligands around the zirconium atoms are close. The crystalline structure determination permits to precise the environment : acetate groups are always bridging and propoxy groups can be bridging or terminal. Clusters containing 9 zirconium atoms, bridged by oxygen atoms, exist in the structure. The colloid size growth was performed by light scattering. A discussion of the role of acetic acid and the competition between the possible reactions is given.

Endogenous gastric mucosal prostaglandins: their role in mucosal integrity

1982 ◽  
Vol 242 (4) ◽  
pp. G337-G341
Author(s):  
M. Ligumsky ◽  
M. I. Grossman ◽  
G. L. Kauffman
Keyword(s):  
Salicylic Acid ◽  
Acetylsalicylic Acid ◽  
Ex Vivo ◽  
Potential Difference ◽  
Fundic Mucosa ◽  
Mucosal Integrity ◽  
Cationic Flux

These studies were designed to determine the role of endogenous gastric mucosal prostaglandins (PG) in maintaining mucosal integrity. Vagally denervated, separated pouches of gastric fundic mucosa in unanesthetized dogs were irrigated with either acetylsalicylic acid (ASA) or salicylic acid (SA) (0, 2.5, 5.0, 10.0, 20.0, and 40.0 mM) in 150 mM HCl. Transmucosal potential difference (PD) and net H+, Na+, and K+ flux were measured. Mucosal ex vivo generation of 6-oxo-PGF1 alpha, PGE2, and PGF2 alpha was measured by radioimmunoassay in mucosal biopsies taken after exposure to each agent. No difference in PD or net H+, Na+, or K+ flux was observed between pouch irrigation with ASA or SA at 2.5-20.0 mM concentrations. Net H+ and Na+ flux was significantly greater (P less than 0.01) after irrigation with 40 mM SA than with 40 mM ASA. No significant reduction in gastric mucosal ex vivo generation of 6-oxo-PGF1 alpha (range, 65-98 ng.g-.min-1), PGE2 (range, 250-326 ng.g-1.min-1), or PGF2 alpha (range, 115-156 ng.g-1.min-1) was observed after pouch irrigation with all concentrations of SA. In comparison, gastric mucosal ex vivo generation of 6-oxo-PGF1 alpha (range, 75-2 ng.g-1.min-1), PGE2 (range, 22-3 ng.g-1.min-1), and PGF2 alpha (range, 40-2 ng.g-1.min-1) was significantly reduced after irrigation with all concentrations of ASA. From these data, we conclude that the activity of endogenous gastric prostacyclin, PGE2 alpha, and PGF2 alpha is not a prerequisite for mucosal integrity as measured by PD and net cationic flux.

scholarly journals Combined effect of Cr+6 and chelating agents on growth and Cr bioaccumulation in flood susceptible variety of rice Oryza sativa (L.) cv. Swarna

2017 ◽  
Vol 6 (2) ◽  
pp. 1573 ◽  
Author(s):  
Purnaprava Mantry* ◽  
Hemanta Kumar Patra
Keyword(s):  
Acetic Acid ◽  
Salicylic Acid ◽  
Oryza Sativa ◽  
Citric Acid ◽  
Water Deficit ◽  
Chelating Agents ◽  
Oryza Sativa L ◽  
Susceptible Variety ◽  
Rice Seedlings

Flood susceptible variety of Rice (Swarna) were grown in both water logged & water deficit condition. The experimental seedlings were treated with Cr+6 (10mg) and Cr+6 (50mg) both in the presence & in the absence of chelating agents (EDTA-Ethylene Diamine Tetra Acetic Acid, SA-Salicylic Acid, CA-Citric Acid). The results showed that the enhancement of Cr bioavailability in plants occurs by supplementing Cr+6 with chelating agents. This clearly depicts that the role of chelating agents increases the toxic effects of Cr+6 simultaneously increasing the rate of Cr accumulation in rice seedlings.

Increased blood plasma hydrolysis of acetylsalicylic acid in type 2 diabetic patients: A role of plasma esterases

2006 ◽  
Vol 1760 (2) ◽  
pp. 207-215 ◽  
Author(s):  
Peter Grešner ◽  
Martin Dolník ◽  
Iveta Waczulíková ◽  
Maria Bryszewska ◽  
Libuša Šikurová ◽  
...  
Keyword(s):  
Acetylsalicylic Acid ◽  
Blood Plasma ◽  
Diabetic Patients ◽  
Type 2 Diabetic Patients ◽  
Hydrolysis Of ◽  
Type 2 Diabetic

scholarly journals Mechanistic consequences of replacing the active-site nucleophile Glu-358 in Agrobacterium sp. β-glucosidase with a cysteine residue

1998 ◽  
Vol 330 (1) ◽  
pp. 203-209 ◽  
Author(s):  
L. Sherry LAWSON ◽  
J. R. Antony WARREN ◽  
G. Stephen WITHERS
Keyword(s):  
Rate Constant ◽  
Active Site ◽  
Cysteine Residue ◽  
Kinetic Evaluation ◽  
Glycosidic Bonds ◽  
Proposal A ◽  
Leaving Group ◽  
Hydrolysis Of ◽  
Enzyme Intermediate

Retaining glycosidases achieve the hydrolysis of glycosidic bonds through the assistance of two key active-site carboxyls. One carboxyl functions as a nucleophile/leaving group, and the other acts as the acid-base catalyst. It has been suggested that a cysteine residue could fulfil the role of the active site nucleophile [Hardy and Poteete (1991) Biochemistry 30, 9457-9463]. To test the validity of this proposal, a kinetic evaluation was conducted on the active-site nucleophile cysteine mutant (Glu-358 → Cys) of the retaining β-glucosidase from Agrobacterium sp. The Glu-358 → Cys mutant was able to complete the first step (glycosylation) of the enzymic mechanism, forming a covalent glycosyl-enzyme intermediate, but the rate constant for this step was decreased to 1/106 of that of the native enzyme. The subsequent hydrolysis (deglycosylation) step was also severely affected by the replacement of Glu-358 with a cysteine residue, with the rate constant being depressed to 1/107 or less. Thus Cys-358 functions inefficiently in both the capacity of catalytic nucleophile and leaving group. On the basis of these results it seems unlikely that the role of the active-site nucleophile in retaining glycosidases could successfully be filled by a cysteine residue.

The neutral hydrolysis of methyl acetate — Part 1. Kinetic experiments

2009 ◽  
Vol 87 (4) ◽  
pp. 539-543 ◽  
Author(s):  
Yih-Huang Hsieh ◽  
Noham Weinberg ◽  
Saul Wolfe
Keyword(s):  
Acetic Acid ◽  
Hydrochloric Acid ◽  
Rate Constant ◽  
Rate Constants ◽  
Methyl Acetate ◽  
Acid Catalysis ◽  
Acid Product ◽  
Neutral Reaction ◽  
Uncatalyzed Reaction ◽  
Hydrolysis Of

The neutral hydrolysis of methyl acetate and catalysis of the reaction by the acetic acid product have been studied in the temperature range 90–110 °C. Extrapolated to 25 °C, the rate constants are 0.17 × 10−8 s–1 for the uncatalyzed reaction and 1.4 × 10−4 (mol/L)–1s–1 for the catalyzed reaction. The acid catalysis is specific not general: at 90 °C the rate constants for hydrochloric acid catalysis and catalysis by ionized acetic acid are the same as the rate constant, kH = 1.4 × 10−2 (mol/L)–1s–1, determined in the neutral reaction.

scholarly journals THE BIOCHEMISTRY OF THE USTILAGINALES: III. THE DEGRADATION PRODUCTS AND PROOF OF THE CHEMICAL HETEROGENEITY OF USTILAGIC ACID

1951 ◽  
Vol 29 (5) ◽  
pp. 415-425 ◽  
Author(s):  
R. U. Lemieux
Keyword(s):  
Acetic Acid ◽  
Methyl Ester ◽  
Caprylic Acid ◽  
Degradation Products ◽  
Caproic Acid ◽  
Specific Rotation ◽  
Chemical Heterogeneity ◽  
Hydroxy Acids ◽  
Hydrolysis Of ◽  
Derivatives Of

The D-glucolipid designated as ustilagic acid was shown to be a mixture of partially acylated derivatives of a di-D-glucosyl-dihydroxyhexadecanoic acid. The dihydroxyhexadecanoic acid was named "ustilic acid" and its di-D-glucosyl derivative was termed "glucoustilic acid". Alkaline hydrolysis of ustilagic acid yielded glucoustilic acid, acetic acid, dextro-β-hydroxy-n-caproic acid, dextro-β-hydroxy-n-caprylic acid and a small amount of n-caproic acid. The β-hydroxy-acids were characterized as dextro-β-hydroxy-n-caprohydrazide, m.p. 131–132°C., [α]D + 15.9° (water), and dextro-β-hydroxy-n-caprylhydrazide, m.p. 127–128°C., [α]D + 12° (water). Ustilic acid, m.p. 114–115°C., [α]D − 6.3° (methanol), yielded a methyl ester, m.p. 80−81.8°C, [α]D − 0.2 (chloroform). The methyl ustilate formed a di-phenylurethane derivative, m.p. 76–77°C. The infrared spectra of crystalline and amorphous samples of ustilagic acid are given. The specific rotation of glucoustilic acid, [α]D − 11° (methanol) was that expected of β-D-glucosides and the infrared spectrum of this substance showed a marked resemblance to that of methyl-β-D-glucopyranoside.

Sign in / Sign up

Export Citation Format

Share Document